HbA1c, glucose and insulin: reading them together

The UAE has one of the highest rates of type 2 diabetes in the world. The International Diabetes Federation puts adult prevalence at roughly one in five, and a large share of those people do not know they have it. Diabetes does not arrive overnight. It is the end of a process that runs for a decade or more, and most of that process is visible in a blood test if the right markers are measured and read together. This post explains the three that matter, HbA1c, fasting glucose and fasting insulin, and why reading any one of them alone is the mistake most check-ups make.

Fasting glucose: the snapshot

Fasting glucose is the sugar in your blood after an overnight fast. It is the marker on every basic panel and it is genuinely useful, but it is a single moment. It rises with a bad night's sleep, an infection, or stress, and it is one of the last things to change as insulin resistance develops, because the body works very hard to keep it in range.

• Below 5.6 mmol/L (100 mg/dL) is normal.
• 5.6 to 6.9 mmol/L (100 to 125 mg/dL) is impaired fasting glucose, often called prediabetes.
• 7.0 mmol/L (126 mg/dL) or above on two occasions is one of the diagnostic criteria a doctor uses.

HbA1c: the three-month average

HbA1c is the share of haemoglobin in your red blood cells that has sugar attached to it. Red cells live around 120 days, so the figure reflects average blood sugar over roughly three months. It smooths out the noise in a single fasting reading and it does not require fasting.

• Below 5.7% (39 mmol/mol) is normal.
• 5.7% to 6.4% (39 to 47 mmol/mol) is the prediabetes range.
• 6.5% (48 mmol/mol) or above is a diagnostic threshold, again for a doctor to interpret.

HbA1c has one blind spot worth knowing about. Anything that changes how long red cells live changes the number. Iron deficiency anaemia, which is common in the UAE, can push HbA1c up. Some inherited haemoglobin variants found in the region can push it down. That is why the panel reports ferritin and a full blood count beside it.

Fasting insulin: the early warning

Insulin is the hormone that moves sugar out of the blood. As cells become less responsive to it, the pancreas makes more to compensate. For years, sometimes a decade, glucose stays normal while insulin climbs. That period is insulin resistance, and it is when the most useful changes can be made.

A basic panel never measures insulin. There is no single agreed normal range for fasting insulin. Each laboratory sets its own, and insulin methods are not fully standardised, so the same sample can give different numbers in different laboratories and a result is read against the range on its own report. Values well above that range with a normal glucose are the classic early pattern.

HOMA-IR: putting the two together

HOMA-IR combines fasting glucose and fasting insulin into a single estimate of insulin resistance. It is calculated, not measured, and Clare labels it as such. There is no agreed cut-off. Proposed values differ with the population studied, the insulin method and the definition of insulin resistance used: 1.62 in a study of Arab adults in Oman, and 2.05 or 3.46 in a Spanish population study, depending on the definition. If the report gives a range, the result is read against it, and with a doctor. The TyG index does something similar using triglycerides and glucose, and is useful because it does not depend on an insulin assay.

Why the UAE pattern is different

Several things make insulin resistance more common here than the global average, and they are worth naming because they are the things a plan can change.

• Heat and indoor living. For much of the year walking is not the default, and daily step counts in Gulf cities are among the lowest measured anywhere.
• Vitamin D. Despite the sun, low vitamin D is widespread because of covered clothing, air conditioning and sun avoidance, and low vitamin D is associated with worse insulin sensitivity.
• Sleep. Late evenings, early starts and shift work shorten sleep, and even a single short night measurably raises next-morning glucose and insulin.
• Diet. Sweetened drinks, dates in quantity and large late dinners all raise the insulin load.
• Genetics. South Asian and Arab populations develop insulin resistance at lower body weights than European populations, so a normal BMI is not reassurance.

What to do with the result

If glucose and HbA1c are normal and insulin is high, you are in the window where change works best and where almost nobody is told to change anything. The levers are unglamorous: more walking, more muscle, more sleep, less sugar in liquid form, and a retest.

If HbA1c is in the prediabetes range, the same levers apply and the conversation with a doctor is worth having now rather than in five years. If a value crosses a diagnostic threshold, that is a clinical decision and the laboratory and a clinician are the right people to make it. Clare will say so.

What a retest shows

Fasting insulin can fall within weeks of a real change in activity and diet. HbA1c takes about three months to fully reflect a change, because that is how long it takes the red cell population to turn over. A retest around six months after the first panel is therefore the right interval to see both move. That comparison, not the first number, is the point of testing.